1. Field of the Invention
The invention relates to an arrangement for detecting an object containing an impact sound-receiver for detection of impact sound produced by the object and transmitted in a sound-conducting medium to the receiver, and containing an evaluation circuit which receives an output signal from the receiver and delivers a warning signal when this output signal fulfills predetermined criteria, as well as to the use of this arrangement, especially for determining an approaching train.
2. Description of the Related Art
Such an arrangement is known, for example, from Swiss Patent No. 643,078. It serves for detecting an intruder during an attempt to break through a wall or a safe door in that there are detected impact sound-vibrations transmitted through the brickwork, wall or door serving as sound-conducting medium to the impact sound-receiver and processed by the evaluation circuit. With this arrangement, the signal evaluation is accomplished such that there are reliably distinguished the vibrations arising during an intrusion attempt from spurious vibrations emanating from the surroundings and there is avoided giving of a false alarm signal. In this regard it is attempted to suppress the delivery of a signal for such length of time until it is ensured that the received impact sound really has been caused by an intrusion attempt.
For other uses where, for example, an object which generates an impact sound with continuously increasing or decreasing intensity, must be indicated in all events, and a short-time faulty signal output caused by possible spurious vibrations can be absolutely tolerated, the aforementioned known arrangements are only suitable to a limited extent. In those situations, there was previously preferred purely human monitoring which is frequently unreliable and oftentimes resulted in serious accidents.